Dental articles including a ceramic and microparticle coating and method of making the same

ABSTRACT

Provided are methods of improving the wear resistance and aesthetic properties of dental articles though use of ceramics and microparticles, as well as dental articles having an abrasion resistant microparticle and ceramic coating thereon.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/US2011/0469203 filed Aug. 8, 2011,which claims priority to U.S. Provisional Application No. 61/372,784,filed Aug. 11, 2010. The disclosures of both applications areincorporated by reference in their entirety herein.

BACKGROUND

Flexible metal articles are desirable for treatment of a variety ofdental maladies. Such articles have proven reasonably durable over bothshort-term and long-term dental treatment. Dental articles made from orincluding a malleable metal substrate may typically be modified chairside to adapt to the tooth structures of a particular patient and ensurea secure installation. This degree of post-manufacturing freedom hasmade malleable metal especially popular as dental crowns and orthodonticbands.

Metal crowns, particularly those made of stainless steel are well suitedfor children, as their reasonable life span coincides with the naturalloss of children's teeth. The metallic sheen of stainless steel,however, is not exactly aesthetically appealing. Accordingly, attemptshave been made to apply aesthetic coatings to stainless steel crowns,but these efforts have experienced little success in maintainingflexibility and durability.

SUMMARY

Stainless steel and most other untreated or uncoated metals have becomeincreasingly unappealing to patients desiring high-quality aesthetics inaddition to high performance and durability. Accordingly, there is anincreased demand for dental articles that match or mimic the naturalcolor of teeth. Attempts to meet this demand, including coating withpolymer resins, have been thus far been less than desirable. In someprior art solutions, the coating does not sufficiently adhere to thesurface during the entirety of treatment or the coating becomes easilystained upon exposure to food. In other prior art solutions, therequired coating is so thick that the crown may not be freelymanipulated without cracking, potentially requiring substantial removalof the tooth structure for seating the crown. Such substantial removalmay lead to increased patient sensitivity and other complications.

The dental articles of the present disclosure include an abrasionresistant hybrid coating on at least a portion of the article's outersurface. The abrasion resistant coating of the present disclosureexhibits improved wear and stain resistance while maintaining aestheticappeal during the full period of treatment. The coating of the presentdisclosure further provides a smooth outer surface for the dentalarticle, reducing patient discomfort upon tongue or lip contact.

Unlike previous aesthetic dental articles, the abrasion resistant hybridcoated dental articles maintain desired flexibility such that they maybe cut, bent, crimped, or otherwise manipulated by a practitionerwithout delamination or other failure. Therefore, use of the coateddental articles may allow a dental or orthodontic practitioner toprecisely modify the fit or shape of the dental article withoutsacrificing performance or appearance.

Abrasion resistant hybrid coated dental articles of the presentdisclosure may be crimped and/or otherwise manipulated withoutdeleteriously affecting the aesthetics or performance of the coating.The coating is desirably sufficiently thin on the outer surface so as tobe pliable enough to undergo manipulation without damage or failure.Preferably, the coating is also sufficiently thick in order to withstandtypical mastication (i.e., chewing) and oral preventive care (e.g.,brushing) forces throughout the life of the article. The abrasionresistant hybrid coating includes a ceramic material, a hardenabledental composition, and a plurality of spherical microparticles.

As used herein, the term “hardenable” refers to a material that can becured or solidified, e.g., by heating to remove solvent, heating tocause polymerization, chemical crosslinking, radiation-inducedpolymerization or crosslinking, or the like.

As used herein, “curing” means the hardening or partial hardening of acomposition by any mechanism, e.g., by heat, light, radiation, e-beam,microwave, chemical reaction, or combinations thereof.

As used herein, “dental article” means an article that can be adhered(e.g., bonded) to an oral surface (e.g., a tooth structure). Examplesinclude, but are not limited to, replacements, inlays, onlays, veneers,full and partial crowns (both temporary and permanent), bridges,implants, implant abutments, copings, dentures, posts, bridge frameworksand other bridge structures, abutments, orthodontic appliances anddevices including, but not limited to archwires, buccal tubes, bracketsand bands, and prostheses (e.g., partial or full dentures).

As used herein, the term “ethylenically unsaturated compound” is meantto include monomers, oligomers, and polymers having at least oneethylenic unsaturation.

As used herein, the term “nanofiller” means a filler having an averageprimary particle size of at most 200 nanometers. The nanofillercomponent may be a single nanofiller or a combination of nanofillers.

As used herein, the term “(meth)acrylate” is a shorthand reference toacrylate, methacrylate, or combinations thereof, and “(meth)acrylic” isa shorthand reference to acrylic, methacrylic, or combinations thereof.As used herein, “(meth)acrylate-functional compounds” are compounds thatinclude, among other things, a (meth)acrylate moiety.

As used herein, “phosphorylated monomer” refers to a monomer (e.g., a(meth)acrylate) that comprises at least one phosphate or phosphonategroup.

As used herein, the term “thermal initiator” means a species capable ofefficiently inducing or causing polymerization or crosslinking byexposure to heat.

As used herein, “occlusal” means in a direction toward the outer tips ofthe patient's teeth.

As used herein, “gingival” means in a direction toward the patient'sgums or gingiva.

As used herein, “proximal surface” means the surface nearest to theadjacent tooth.

As used herein, “interproximal” means between the proximal surfaces ofadjoining teeth.

As used herein, “anterior crown” means a crown intended to replaceincisor and canine teeth.

As used herein, “continuous” means extending substantially across atarget surface and including no deliberate gaps or interruptions otherthose inherent in the material.

As used herein, “height of contour” means the point of greatestconvexity of a tooth or crown.

As used herein, deposited or disposed “substantially above the height ofcontour” and variations mean little to no coating is deliberatelydeposited the below the height of contour.

As used in the claims, “filler” means nanofiller, other filler, andcombinations thereof.

As used herein, “average microparticle diameter” and variations thereofrefers to the size of about 50 percent or more of the microparticles inthe coating.

As used herein, “a,” “an,” “the,” “at least one,” and “one or more” areused interchangeably. Thus, for example, a hardenable composition thatcomprises “a” flexible monomer can be interpreted to mean that thehardenable composition includes “one or more” flexible monomers.

As recited herein, all numbers should be considered modified by the term“about”.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.).

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexhaustive list.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described with reference to the drawings,wherein corresponding reference characters indicate corresponding partsthroughout the several views, and wherein:

FIG. 1 is a perspective view of a stainless steel crown.

FIG. 2 is a front plan view of a coated stainless steel crown accordingto an embodiment of the present invention.

FIG. 3 is a cross-sectional view of the stainless steel crown of FIG. 2.

FIG. 4 is a cross-sectional view of a stainless steel crown according toan embodiment of the present disclosure.

FIG. 5 is an enlarged frontal view of a cross-section of a coatedstainless steel crown according to an embodiment of the presentdisclosure.

FIG. 6 is an enlarged frontal view of a cross-section of a coatedstainless steel crown according to a further embodiment of the presentdisclosure.

Layers in the depicted embodiments are for illustrative purposes onlyand are not intended to define the thickness, relative or otherwise, orthe location of any component.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The dental articles of the present disclosure include an abrasionresistant hybrid coating on at least a portion of the article's outersurface. The abrasion resistant hybrid coatings of the presentdisclosure exhibits improved wear and stain resistance while maintainingaesthetic appeal during the full period of treatment. Unlike previousaesthetic dental articles, the abrasion resistant hybrid coated dentalarticles maintain desired flexibility such that they may be cut, bent,crimped, or otherwise manipulated by a practitioner without delaminationor other failure. Therefore, use of the coated dental articles allows adental or orthodontic practitioner to precisely modify the fit or shapeof the dental article without sacrificing performance or appearance.

A coated dental article according to one embodiment of the presentdisclosure is a stainless steel crown (SSC). A typical SSC isconstructed from a preformed base material crown 10 composed ofstainless steel, which is placed in the mouth to cover a prepared tooth12 as shown in FIG. 1. The prepared tooth 12 is shown as having itssurface ground away sufficient for the placement of the crown 10thereon. The scale of the teeth shown and the crown 10 to be placedthereon is for ease of illustration and should not be considered to beat the correct scale. Furthermore, the portion of the tooth 12, whichhas been ground away, is also for illustration purposes only. As shownin FIG. 1, the base metal crown 10, which as shown for illustrationpurposes, is not a molar, and therefore can be pictured generally as aflattened bowl which is formed in the shape of a tooth with an open end16 for placement over the prepared tooth 12. Proper tooth preparationincludes removing all caries and proper shaping of the remaining naturaltooth 12 to receive the SSC 10. Therefore, the prepared tooth 12 istypically left in place in the mouth so that its root provides anchor inthe jaw for the SSC 10. The SSC 10 shown in FIG. 1 is an anterior crown;however, it is to be understood that the present disclosure isapplicable to both anterior and to posterior crowns as well.

Typically an SSC is shaped to resemble the tooth that it replaces and issized to fit comfortably over the portion of the tooth on which thedental procedure is being performed. The crown is trimmed so that thebottom edge of the crown meets the gum line in a comfortable mannerapproximating the placement of the tooth when the crown is applied. Thecrowns are manufactured in sizes and shapes to fit the various types ofteeth. The stainless steel is preferably malleable so it can be crimpedaround the base of the tooth and shaped on the occlusal surface toprovide a comfortable bite with the opposing tooth. Precise adjustmentsby a practitioner to the shape and/or size the SSC are often, though notalways, made to the portion of the SSC below the height of contour 14.

Commercially available preformed stainless steel crowns can be obtainedfrom 3M Company, St. Paul, Minn. Other sources of preformed stainlesssteel crowns include Acero XT, Dallas, Tex. and Denovo Dental, BaldwinPark, Calif.

The preformed base metal in a SSC is typically constructed of coldrolled stainless steel. Prior to coating, the crown can be prepared toremove oil or other surface contaminants by vapor degreasing, alkalinecleaning, acetone cleaning, or ultra-sonic cleaning, for example, asneeded. Surface oxides may be removed and surface activation can beaccomplished by acid treatment or abrasive blasting, for example, asdescribed in more detail below.

Typical stainless steel materials used to construct stainless steelcrowns useful in the present disclosure include AISI-Types 304, 305, and316 stainless steel sheeting (based on the American Iron and SteelInstitute Classification of Chromium-Nickel Stainless Steels). Suchsheeting includes a metal alloy of iron, chromium, and nickel typicallywith small or trace amounts of manganese, carbon, titanium, aluminum,silicon, tantalum, and molybdenum.

FIG. 2 depicts a front plan view of an aesthetic posterior SSC 20,including a abrasion resistant hybrid coating 22. The exterior of thecrown includes a height of contour 26 extending across the wall surface28 below occlusal surface 30 as it transitions into an integralcircumferential area or continuous wall. In the depicted embodiment,portions of the cervical margin, including those proximate thegingival-labial and the gingival-lingual edge regions 32 may be leftuncoated to allow for more precise manipulation and trimming. It isfurther contemplated that the entire outer surface of the SSC may becoated with the abrasion resistant hybrid coating, including thecervical margins.

Though not depicted, it is also contemplated that the coatings of thepresent disclosure be used on anterior crowns. In some embodiments, theentire outer surface of the anterior crown may be coated. In otherembodiments, only the portion of the anterior crown coming into contactwith the opposing dentition (e.g., incisal surface) or the portion abovethe height of contour need be coated. Other portions of an anteriorcrown may be coated as desired.

FIG. 3 illustrates a cross-sectional view of the coated SSC 20 of FIG.2. The outer surface may be primed to include micro texture (e.g.,abraded, deposited, or etched) according to methods described herein. Aceramic layer 34 including a ceramic material is disposed on the surface30. As depicted in FIG. 3, the ceramic layer is continuous over theentire coated surface. The ceramic layer may be disposed on the entireouter surface of the crown, substantially above the height of contour,or some other portion of the crown. The ceramic material is directlybonded, by e.g., an intimate chemical or mechanical interaction, to thetarget surface.

A plurality of spherical microparticles 36 are embedded in a firstpolymeric layer 38. As depicted, the microparticles are distributedacross the occlusal surface 30, with little to no coverage below theheight of contour 26. In the depicted embodiment, at least one sphericalmicroparticle is in close proximity to, if not intimate contact with,the ceramic layer 34. In other embodiments, one or more of the sphericalmicroparticles may be “suspended” in one or more polymeric layers (i.e.,no portion of the microparticle is in contact with the ceramic layer 34or the outer surface of the crown).

The average microparticle is at least 20 microns in diameter, morepreferably at least 30 microns, and even more preferably at least 50microns. Furthermore, the average microparticle diameter is no greaterthan 300 microns, more preferably no greater than 200 microns, and evenmore preferably no greater than 100 microns. Microparticles having anaverage diameter less than 20 microns may be difficult to sufficientlydistribute in a polymeric layer and may not result in sufficient wearresistance. Microparticles larger than 300 microns may require a muchthicker polymeric coating, leading to potential decreases in flexibilityand patient comfort.

In some embodiments, the size distribution of microparticles is narrow,in that the diameter does not differ more than 20% betweenmicroparticles. In other embodiments, the plurality of sphericalmicroparticles includes a greater distribution of varying particlediameters. For example, the plurality of particles may comprise amixture of particles a portion of which has an average particle diameterof 70 microns, and a portion of which has an average particle diameterof 50 microns.

The first polymeric layer 38 includes a first hardened dentalcomposition and is disposed on a portion of outer surface of the SSC, aportion of the ceramic layer 34, and a portion of the sphericalmicroparticles 36. As depicted in FIG. 3, the first polymeric layer 34is continuous over the entire outer surface. As depicted in FIG. 3, boththe ceramic and polymeric layers (34, 38) cover the entire outer surfaceof the SSC 20, with the ceramic and polymeric layers in intimate contacton the wall surfaces below the height of contour 26. It is alsocontemplated, though not depicted in FIG. 3, that either the ceramiclayer 34 or first polymeric layer only extend across the occlusalsurface 30 above the height of contour 26 or some other portion of crownsurface less than the entire outer surface.

One or more additional polymeric layers are also contemplated (thoughnot depicted), so that a coated dental article may include a pluralityof polymeric layers. Suitable additional polymeric layers include thosedescribed in co-pending application entitled, POLYMER COATED DENTALARTICLES AND METHOD OF MAKING THE SAME, International Patent ApplicationNumber PCT/US2011/046909, filed on Aug. 8, 2011.

In some embodiments, the thickness of the coating layer is substantiallyconsistent over the entire coated surface of the dental article. Inother embodiments, the coating may include a thickness gradient. Such agradient may include a gradual decrease or an abrupt decrease in coatingthickness, or a combination thereof. For example, the thickness of thecoating on the occlusal surface 30 may be greater than the thickness ofthe coating on the wall surfaces 28 (e.g., the interproximal surfaces)proximate the height of contour. Further, the coating thickness may thenapproach zero as the cervical margin is approached in a gingivaldirection. It is also contemplated that the thickness of the coating onthe occlusal surface 30 be less than the thickness of the coating on thewall surfaces 28.

In most embodiments, the total thickness 40 of the hardened polymericlayer(s) and ceramic layer 34 on the occlusal surface is at least theaverage diameter of the spherical microparticles 36. While it isappreciated that the total coating thickness may be less than theaverage microparticle diameter in some embodiments, such coatings may besusceptible to increased wear and aesthetic degradation as the sphericalmicroparticles are eventually removed by shear force during the act ofchewing. In some embodiments, the total thickness 40 on the occlusalsurface is at least twice (2×) the average microparticle diameter. Inmost embodiments, the total polymeric thickness is no greater than fivetimes (5×) the average microparticle diameter. Coatings having a totalpolymeric thickness greater than 5× may not be sufficiently flexible forpractitioner manipulation.

The ceramic layer should be sufficiently thick to ensure wear resistanceand aesthetic preferences. In one embodiment, the ceramic layer is atleast 10 microns thick. In a further embodiment, the ceramic layer is atleast 55 microns thick. In a stainless steel crown including a thicknessgradient as described above, it should be appreciated that the minimumthickness is in reference to the thickness of the ceramic layer 34 onthe occlusal surface 30. In one embodiment, the thickness 20 of theceramic layer is no greater than 150 microns. In a further embodiment,the thickness of the ceramic layer is no greater than 100 microns. In afurther embodiment, the thickness of the ceramic layer is no greaterthan 75 microns.

In one embodiment, the thickness of the one or more polymeric layers isno less than 5 microns. In another embodiment, the thickness of the oneor more polymeric layers is no less than 10 microns. In a furtherembodiment, the thickness of the one or more polymeric layers is no lessthan 20 microns. In one embodiment, the thickness of the one or morepolymeric layers is no greater than 300 microns. In another embodiment,the thickness of the one or more polymeric layers is no greater than 150microns. In a further embodiment, the thickness of the one or morepolymeric layers is no greater than 50 microns.

As noted above, the thickness of the coating may approach zero onportions of the gingival or interproximal surfaces. In certainembodiments, the thickness of the coating on the wall surfaces below theheight of contour is no greater than 150 microns, in other embodimentsless than 100 microns, in yet other embodiments less than 50 microns. Ina further embodiment, the thickness of the coating on the wall surfacesbelow the height of contour is no greater than 30 microns. Thicknessesexceeding 150 microns may not provide sufficient flexibility in certainembodiments.

The arrangement of the spherical microparticles may be furtherunderstood with reference to FIG. 4. As depicted, the sphericalmicroparticles are spaced from one another, as measured on an edge toedge basis (identified in FIG. 4 by numerical indicator 42), on theorder of the average diameter of the microparticles used. The averagespacing may be between close packed (microparticles are touching or arenearly touching) and five times the average microparticle diameter.Though contemplated, bead spacing that approaches closely packedconditions may adversely affect the aesthetic properties of a coatedcrown due to the relative predominance of beads and resultant reductionin the amount/coverage of polymeric/ceramic coating. Microparticles thatare too closely packed may further reduce the flexibility and polymeradhesion. In certain embodiments, the average spacing is between onequarter of the average diameter and three times the average diameter. Inpreferred embodiments, the average spacing is between one quarter of theaverage diameter and two times the average diameter.

In certain embodiments, the spacing between microparticles issubstantially uniform. In other embodiments, the microparticles can bemore randomly distributed.

Alternatively, from 3% by weight to 90% by weight of the microparticlesare present in the coating, more preferably, from 7% to 60% by weightbased on the weight of the entire coating (i.e., sphericalmicroparticles and all ceramic and polymeric layers) in the area wherebeads are present.

As noted above, the ceramic layer can be discontinuous (e.g., patterned)on the coated surface of the SSC. One embodiment of a discontinuousceramic layer 50 on a surface is illustrated in FIG. 5. Such adiscontinuous layer includes gaps 52 (i.e., pores or apertures) betweendeposits of ceramic material 54. In the depicted embodiment, thepolymeric layer 56 (or polymeric layers) partially or completely fillsthe gaps 52 between the ceramic deposits 54. In some embodiments, thespherical microparticles 58 partially fill at least some of the gaps 52.In other embodiments, wherein gaps are larger than the averagemicroparticle diameter, at least some of the microparticles maycompletely fill at least some of the gaps 52. Without wishing to bebound by theory, the gaps 52 in the discontinuous ceramic layer mayimprove appearance and flexibility, as well as improve the adhesion ofthe one or more polymeric layers to the dental article surface.

In some embodiments, the discontinuous ceramic layer includes anidentifiable pattern of alternating gaps and ceramic deposits. In otherembodiments, the ceramic layer is irregular or otherwise non-patterned(e.g., varying distances between deposits). Other embodiments mayinclude a combination of patterned and non-patterned sections of theceramic layer.

It is also contemplated that the ceramic layer may be substantiallycontinuous over at least a portion of the outer surface, but maycomprise discrete ceramic sections of varying thickness. Such anembodiment is depicted in FIG. 6. The ceramic layer 60 includes apparentpeaks 64 and valleys 62. The valleys 62 (i.e., areas of the surface havea thinner coating section) may be sufficiently thin so as to enableflexibility of the overall construction. In one embodiment, the pitch ofthe structured ceramic surface (i.e. the distance between repeatingpeaks 64) may be on a length-scale such that it is not readily visibleto the unassisted eye. Accordingly, the pitch in one embodiment is 0.2mm, in another embodiment 0.1 mm, and in a further embodiment 0.05 mm.Furthermore, the ratio of the area of the valleys 62 to the area of thepeaks 50 in the structured surface in one embodiment may be at least0.3, in another embodiment at least 0.5 and in a further embodiment atleast 0.7.

Without wishing to be bound by theory, a hardenable composition of theone or more polymeric layers may penetrate openings in continuous (e.g.,micropores) and discontinuous layers form an interpenetrating network(IPN).

Suitable ceramic materials for use in a ceramic layer include, but arenot limited to, alumina, zirconia, yttria, yttria-stabilized zirconia,porcelain, blends and other combinations thereof.

In certain embodiments, the spherical microparticles include aninorganic material. Suitable materials for use as inorganic sphericalmicroparticles include ceramics and glass-ceramics. Suitable materialsfor use as inorganic spherical microparticles include, but are notlimited to, alumina, zirconia, yttria, yttria-stabilized zirconia,porcelain, blends and other combinations thereof. Particularly usefulyttria-stabilized zirconia spherical microparticles are available fromGlen Mills, Inc., Clifton, N.J.

Exemplary hardenable compositions useful for creating the one or morepolymeric layers include at least one of a polymerizable component, aninitiator system, a pigment, a nanofiller, a filler, and other additives(e.g., solvents). Particularly useful hardenable dental compositionsexhibit a color similar to a patient's tooth (e.g., ivory) whendeposited on the surface of the dental article, either alone or incooperation with other hardenable dental compositions. The potentialcomponents of the hardenable composition are described in more detailbelow.

Polymerizable Component

The hardenable compositions of the present disclosure are typicallyhardenable due the presence of a polymerizable component. In someembodiments, the compositions can be hardened (e.g., polymerized byconventional photopolymerization and/or chemical polymerizationtechniques) after it has been applied to the surface of a dentalarticle.

In certain embodiments, the compositions are photopolymerizable, i.e.,the compositions contain a photoinitiator system that upon irradiationwith actinic radiation initiates the polymerization (or hardening) ofthe composition. In other embodiments, the compositions are chemicallyhardenable, i.e., the compositions contain a chemical initiator (i.e.,initiator system) that can polymerize, cure, or otherwise harden thecomposition without dependence on irradiation with actinic radiation.Such chemically hardenable compositions are sometimes referred to as“self-cure” compositions.

In other embodiments, the compositions are thermally polymerizable,i.e., the compositions contain a thermal initiator system that uponheating or other application of thermal energy initiates thepolymerization (or hardening) of the composition.

The polymerizable component typically comprises one or moreethylenically unsaturated compounds, with or without acid functionality.Examples of useful ethylenically unsaturated compounds include acrylicacid esters, methacrylic acid esters, hydroxy-functional acrylic acidesters, hydroxy-functional methacrylic acid esters, and combinationsthereof. The polymerizable component may comprise one or moreethylenically unsaturated compounds, with or without acid functionalitythat is phosphorylated, such as a phosphorylated methacrylate.

The compositions, especially in photopolymerizable implementations, mayinclude compounds having free radically active functional groups thatmay include monomers, oligomers, and polymers having one or moreethylenically unsaturated group. Suitable compounds contain at least oneethylenically unsaturated bond and are capable of undergoing additionpolymerization. Such free radically polymerizable compounds includemono-, di- or poly-(meth)acrylates (i.e., acrylates and methacrylates)such as, methyl(meth)acrylate, ethyl acrylate, isopropyl methacrylate,n-hexyl acrylate, stearyl acrylate, allyl acrylate, glyceroltriacrylate, ethyleneglycol diacrylate, diethyleneglycol diacrylate,triethyleneglycol dimethacrylate, 1,3-propanediol di(meth)acrylate,trimethylolpropane triacrylate, 1,2,4-butanetriol trimethacrylate,1,4-cyclohexanediol diacrylate, pentaerythritol tetra(meth)acrylate,sorbitol hexacrylate, tetrahydrofurfuryl(meth)acrylate,bis[1-(2-acryloxy)]-p-ethoxyphenyldimethylmethane,bis[1-(3-acryloxy-2-hydroxy)]-p-propoxyphenyldimethylmethane,ethoxylated bisphenolA di(meth)acrylate, andtrishydroxyethyl-isocyanurate trimethacrylate; (meth)acrylamides (i.e.,acrylamides and methacrylamides) such as (meth)acrylamide, methylenebis-(meth)acrylamide, and diacetone(meth)acrylamide;urethane(meth)acrylates; the bis-(meth)acrylates of polyethylene glycols(preferably of molecular weight 200-500), copolymerizable mixtures ofacrylated monomers such as those in U.S. Pat. No. 4,652,274 (Boettcheret al.), acrylated oligomers such as those of U.S. Pat. No. 4,642,126(Zador et al.), and poly(ethylenically unsaturated) carbamoylisocyanurates such as those disclosed in U.S. Pat. No. 4,648,843(Mitra); and vinyl compounds such as styrene, diallyl phthalate, divinylsuccinate, divinyl adipate and divinyl phthalate. Other suitable freeradically polymerizable compounds include siloxane-functional(meth)acrylates as disclosed, for example, in WO-00/38619 (Guggenbergeret al.), WO-01/92271 (Weinmann et al.), WO-01/07444 (Guggenberger etal.), WO-00/42092 (Guggenberger et al.) and fluoropolymer-functional(meth)acrylates as disclosed, for example, in U.S. Pat. No. 5,076,844(Fock et al.), U.S. Pat. No. 4,356,296 (Griffith et al.), EP-0373 384(Wagenknecht et al.), EP-0201 031 (Reiners et al.), and EP-0201 778(Reiners et al.). Mixtures of two or more free radically polymerizablecompounds can be used if desired.

The polymerizable component may also comprise monomers that are curableby ring-opening metathesis polymerization (ROMP) having at least onefunctionality curable by ROMP, such as at least one endocyclicolefinically unsaturated doublebond. Generally, suitable monomers canfollow the general formula B-A_(n) wherein A is a moiety polymerizableby ROMP such as cyclobutenyl, cyclopentenyl, cyclooctenyl or bicyclicring systems like the often preferred norbornenyl and 7-oxa-norbornenylgroups, and B is an organic or silicon-organic backbone with 1 to 100,e.g., 1 to 10 or 1 to 5 or 1 to 4 moieties polymerizable by ROMP, e.g.,2 or 3 moieties polymerizable by ROMP, are attached, n being 1 to 100.The composition according to the disclosure may contain only one type ofmonomer according to the general formula B-A. It is also possible that acomposition according to the disclosure contains two or more differenttypes of monomers according to the general formula B-A. In someembodiments, the composition contains at least one type of monomeraccording to the general formula B-A_(n), which has one or twoolefinically unsaturated double bonds which are curable by ROMP.Suitable monomers are described, for example, in great detail in USPatent Publication No. 2009/00884 (Luchterhandt et al.).

The polymerizable component may also contain hydroxyl groups andethylenically unsaturated groups in a single molecule. Examples of suchmaterials include hydroxyalkyl(meth)acrylates, such as2-hydroxyethyl(meth)acrylate and 2-hydroxypropyl(meth)acrylate; glycerolmono- or di-(meth)acrylate; trimethylolpropane mono- ordi-(meth)acrylate; pentaerythritol mono-, di-, and tri-(meth)acrylate;sorbitol mono-, di-, tri-, tetra-, or penta-(meth)acrylate; and2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (bisGMA).Suitable ethylenically unsaturated compounds are available from a widevariety of commercial sources, such as Sigma-Aldrich, St. Louis.Mixtures of ethylenically unsaturated compounds can be used if desired.

In certain embodiments, the polymerizable component may include, bisGMA,UDMA (urethane dimethacrylate), GDMA (glycerol dimethacrylate), TEGDMA(triethyleneglycol dimethacrylate), bisEMA6 as described in U.S. Pat.No. 6,030,606 (Holmes), phenoxyethylmethacrylate, and/or NPGDMA(neopentylglycol dimethacrylate). The polymerizable component mayinclude combinations of these hardenable components.

In some embodiments, the polymerizable component may include one or moreethylenically unsaturated compounds with acid functionality. As usedherein, ethylenically unsaturated compounds “with acid functionality” ismeant to include monomers, oligomers, and polymers having ethylenicunsaturation and acid and/or acid-precursor functionality.Acid-precursor functionalities include, for example, anhydrides, acidhalides, and pyrophosphates. The acid functionality can includecarboxylic acid functionality, phosphoric acid functionality, phosphonicacid functionality, sulfonic acid functionality, or combinationsthereof.

Ethylenically unsaturated compounds with acid functionality include, forexample, α,β-unsaturated acidic compounds such as glycerol phosphatemono(meth)acrylates, glycerol phosphate di(meth)acrylates,hydroxyethyl(meth)acrylate (e.g., HEMA) phosphates,bis((meth)acryloxyethyl)phosphate, ((meth)acryloxypropyl)phosphate,bis((meth)acryloxypropyl)phosphate, bis((meth)acryloxy)propyloxyphosphate, (meth)acryloxyhexyl phosphate,bis((meth)acryloxyhexyl)phosphate, (meth)acryloxyoctyl phosphate,bis((meth)acryloxyoctyl)phosphate, (meth)acryloxydecyl phosphate,bis((meth)acryloxydecyl)phosphate, caprolactone methacrylate phosphate,citric acid di- or tri-methacrylates, poly(meth)acrylated oligomaleicacid, poly(meth)acrylated polymaleic acid, poly(meth)acrylatedpoly(meth)acrylic acid, poly(meth)acrylated polycarboxyl-polyphosphonicacid, poly(meth)acrylated polychlorophosphoric acid, poly(meth)acrylatedpolysulfonate, poly(meth)acrylated polyboric acid, and the like, may beused as components in the hardenable component system. Also monomers,oligomers, and polymers of unsaturated carbonic acids such as(meth)acrylic acids, aromatic (meth)acrylated acids (e.g., methacrylatedtrimellitic acids), and anhydrides thereof can be used. Certainembodiments of the composition of the present disclosure include anethylenically unsaturated compound with acid functionality having atleast one P—OH moiety.

Certain of these compounds are obtained, for example, as reactionproducts between isocyanatoalkyl(meth)acrylates and carboxylic acids.Additional compounds of this type having both acid-functional andethylenically unsaturated components are described in U.S. Pat. No.4,872,936 (Engelbrecht) and U.S. Pat. No. 5,130,347 (Mitra). A widevariety of such compounds containing both the ethylenically unsaturatedand acid moieties can be used. Mixtures of such compounds can be used ifdesired.

Additional ethylenically unsaturated compounds with acid functionalityinclude, for example, polymerizable bisphosphonic acids as disclosed forexample, in U.S. Patent Application Publication No. 2009-0075239(Abuelyaman); AA:ITA:IEM (copolymer of acrylic acid:itaconic acid withpendent methacrylate made by reacting AA:ITA copolymer with sufficient2-isocyanatoethyl methacrylate to convert a portion of the acid groupsof the copolymer to pendent methacrylate groups as described, forexample, in Example 11 of U.S. Pat. No. 5,130,347 (Mitra)); and thoserecited in U.S. Pat. No. 4,259,075 (Yamauchi et al.), U.S. Pat. No.4,499,251 (Omura et al.), U.S. Pat. No. 4,537,940 (Omura et al.), U.S.Pat. No. 4,539,382 (Omura et al.), U.S. Pat. No. 5,530,038 (Yamamoto etal.), U.S. Pat. No. 6,458,868 (Okada et al.), and European Pat.Application Publication Nos. EP 712,622 (Tokuyama Corp.) and EP1,051,961 (Kuraray Co., Ltd.).

Compositions of the present disclosure can also include combinations ofethylenically unsaturated compounds with acid functionality asdescribed, for example, in U.S. Patent Application Publication No.2007/0248927 (Luchterhandt et al.)f. The compositions may also include amixture of ethylenically unsaturated compounds both with and withoutacid functionality.

Polymerizable components may also include monomers and multimethacrylateoligomers, including but not limited to,trimethylcyclohexylmethacrylate, C8-C18 monomethacrylates,phenoxyethylmethacrylate, PEGDMA (polyethyleneglycol dimethacrylatehaving a molecular weight of approximately 400), aliphatic urethanemethacrylates, aliphatic polyester urethane methacrylates, aliphaticpolyester triurethane acrylates. Further contemplated are reactionsproducts of polytetramethylene ether diols and/or polycaprolactonepolyols with isocyanatoethylmethacrylate. In certain embodiments, theflexible monomers and/or oligomers have a glass transition temperatureof no greater than 60 degrees Celsius.

Adding the flexible monomers and multimethacrylate oligomers to ahardenable composition can create a composition having improvedflexibility as evidenced by, for example, having at least a 3%elongation to break or ability to bend around at least an 8 mm mandrel.In certain preferred embodiments, the hardenable compositions depositedon wall surfaces below the height of contour include a flexible monomeror oligomer.

An exemplary self-cure system comprising aliphatic polyisocyanates isdescribed in U.S. Pat. Nos. 7,189,429 and 6,730,353 (Robinson). Thefirst part of this two-part system includes one or more aliphaticpolyisocyanates. Suitable polyisocyanates include derivatives ofhexamethylene-1,6-diisocyanate; 2,2,4-trimethylhexamethylenediisocyanate; isophorone diisocyanate; and 4,4′dicyclohexylmethanediisocyanate. Preferred polyisocyanates are the uretdione, biuret andisocyanurate trimer of hexamethylene-1,6-diisocyanate, with theuretdione being particularly preferred.

The preferred polyisocyanates have an isocyanate content of 15 to 30%,with an isocyanate content of 20 to 25% being particularly preferred.The aliphatic polyisocyanates may further be blended with one or moreamine reactive resins and/or non-reactive resins.

The second part of a two-part coating system comprises one or morepolyamines. The one or more polyamines are preferably aromatic. Suitablepolyamines include diethyl toluenediamine; dimethylthio toluenediamine;4,4′-methylenebis(2-isopropyl-6-methylaniline); and4,4′-methylenebis(3-chloro-2,6-diethylaniline). The polyamines mayfurther be blended with polyhydric alcohol. The polyhydric alcoholcompounds can be polyester or polyether polyols containing at least twohydroxyl groups per molecule. Branched polyether-esters are particularlyuseful.

In another embodiment of the two-part coating system, the aromaticpolyamines may be blended with oligomeric polyamines. Suitable compoundsinclude poly(oxypropylene)diamines, poly(oxypropylene)triamines,poly(oxytetramethylene)-di-p-aminobenzoates.

Additional flexible components suitable for use in certain two-partsystems include polyTHF, polyethyleneoxide, and polypropylene oxide.

Initiator Systems

In certain embodiments, the hardenable compositions of the presentdisclosure are photopolymerizable, i.e., the hardenable compositionscontain a photopolymerizable component and a photoinitiator system thatupon irradiation with actinic radiation initiates the polymerization (orhardening) of the composition. Such photopolymerizable compositions canbe free radically polymerizable or cationically polymerizable.

Suitable photoinitiators (i.e., photoinitiator systems that include oneor more compounds) for polymerizing free radically photopolymerizablecompositions include binary and tertiary systems. Typical tertiaryphotoinitiators include an iodonium salt, a photosensitizer, and anelectron donor compound as described in U.S. Pat. No. 5,545,676(Palazzotto et al.). Suitable iodonium salts are the diaryl iodoniumsalts, e.g., diphenyliodonium chloride, diphenyliodoniumhexafluorophosphate, diphenyliodonium tetrafluoroborate, andtolylcumyliodonium tetrakis(pentafluorophenyl)borate. Suitablephotosensitizers are monoketones and diketones that absorb some lightwithin a range of 400 nm to 520 nm (preferably, 450 nm to 500 nm).Particularly suitable compounds include alpha diketones that have lightabsorption within a range of 400 nm to 520 nm (even more preferably, 450to 500 nm). Suitable compounds are camphorquinone, benzil, furil,3,3,6,6-tetramethylcyclohexanedione, phenanthraquinone,1-phenyl-1,2-propanedione and other 1-aryl-2-alkyl-1,2-ethanediones, andcyclic alpha diketones. Suitable electron donor compounds includesubstituted amines, e.g., ethyl dimethylaminobenzoate. Other suitabletertiary photoinitiator systems useful for photopolymerizingcationically polymerizable resins are described, for example, in U.S.Pat. No. 6,765,036 (Dede et al.).

Other useful photoinitiators for polymerizing free radicallyphotopolymerizable compositions include the class of phosphine oxidesthat typically have a functional wavelength range of 380 nm to 1200 nm.Suitable phosphine oxide free radical initiators with a functionalwavelength range of 380 nm to 450 nm are acyl and bisacyl phosphineoxides such as those described in U.S. Pat. No. 4,298,738 (Lechtken etal.), U.S. Pat. No. 4,324,744 (Lechtken et al.), U.S. Pat. No. 4,385,109(Lechtken et al.), U.S. Pat. No. 4,710,523 (Lechtken et al.), and U.S.Pat. No. 4,737,593 (Ellrich et al.), U.S. Pat. No. 6,251,963 (Kohler etal.); and EP Application No. 0 173 567 A2 (Ying).

Commercially available phosphine oxide photoinitiators capable offree-radical initiation when irradiated at wavelength ranges of greaterthan 380 nm to 450 nm include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (IRGACURE 819, Ciba Specialty Chemicals, Tarrytown,N.Y.), bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylpentyl)phosphine oxide(CGI 403, Ciba Specialty Chemicals), a 25:75 mixture, by weight, ofbis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl phosphine oxide and2-hydroxy-2-methyl-1-phenylpropan-1-one (IRGACURE 1700, Ciba SpecialtyChemicals), a 1:1 mixture, by weight, ofbis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide and2-hydroxy-2-methyl-1-phenylpropane-1-one (DAROCUR 4265, Ciba SpecialtyChemicals), and ethyl 2,4,6-trimethylbenzylphenyl phosphinate (LUCIRINLR8893X, BASF Corp., Charlotte, N.C.).

Typically, the phosphine oxide initiator is present in thephotopolymerizable composition in catalytically effective amounts, suchas from 0.1 weight percent to 5.0 weight percent, based on the totalweight of the unfilled composition.

Tertiary amine reducing agents may be used in combination with anacylphosphine oxide. Illustrative tertiary amines useful in thedisclosure include ethyl 4-(N,N-dimethylamino)benzoate andN,N-dimethylaminoethyl methacrylate. When present, the amine reducingagent is present in the photopolymerizable composition in an amount from0.1 weight percent to 5.0 weight percent, based on the total weight ofthe unfilled composition. Useful amounts of other initiators are wellknown to those of skill in the art.

In certain embodiments, the compositions of the present disclosure arechemically hardenable, i.e., the compositions contain a chemicallyhardenable component and a chemical initiator (i.e., initiator system)that can polymerize, cure, or otherwise harden the composition withoutdependence on irradiation with actinic radiation. Such chemicallyhardenable compositions are sometimes referred to as “self-cure”compositions.

In embodiments wherein the hardenable composition includes a monomer oroligomer curable by ROMP, suitable initiators include all substanceswhich are able to initiate a ROMP polymerization in a curablecomposition. It is preferred that a polymer composition comprising anROMP initiator is sufficiently chemically stable at ambient temperature,generally at room temperature or temperatures up to 60° C., providingunhindered preparation and molding of the formulation.

Suitable chemically stable initiators do not lead to an increase ofviscosity of the composition of more than 10% during a minimum of 5hours at temperatures below 50° C. It is also preferred that a suitableinitiator will cure the formulation within 24 hours at a temperatureabove 100° C. by ROMP reaction. Preferred initiators are metal complexesof ruthenium or osmium not bearing a carbene function. Examples ofsuitable initiators can be found in Castarlenas et al., Journal ofOrganometallic Chemistr, 663 (2002) 235-238 and in Hafner et al., Angew.Chem. 1997, 109, Nr. 19, S. 2213. Further preferred initiators aredisclosed in U.S. Pat. No. 6,001,909 (Setiabudi) and US PatentPublication No. 2009/00884 (Luchterhandt et al.).

The chemically hardenable compositions may include redox cure systemsthat include a polymerizable component (e.g., an ethylenicallyunsaturated polymerizable component) and redox agents that include anoxidizing agent and a reducing agent. Suitable polymerizable components,redox agents, optional acid-functional components, and optional fillersthat are useful in the present disclosure are described in U.S. Pat.Publication Nos. 2003/0166740 (Mitra et al.) and 2003/0195273 (Mitra etal.).

The reducing and oxidizing agents should react with or otherwisecooperate with one another to produce free-radicals capable ofinitiating polymerization of the resin system (e.g., the ethylenicallyunsaturated component). This type of cure is a dark reaction, that is,it is not dependent on the presence of light and can proceed in theabsence of light. The reducing and oxidizing agents are preferablysufficiently shelf-stable and free of undesirable colorization to permittheir storage and use under typical dental conditions. They should besufficiently miscible with the resin system (and preferablywater-soluble) to permit ready dissolution in (and discourage separationfrom) the other components of the composition.

Useful reducing agents include ascorbic acid, ascorbic acid derivatives,and metal complexed ascorbic acid compounds as described in U.S. Pat.No. 5,501,727 (Wang et al.); amines, especially tertiary amines, such as4-tert-butyl dimethylaniline; aromatic sulfinic salts, such asp-toluenesulfinic salts and benzenesulfinic salts; thioureas, such as1-ethyl-2-thiourea, tetraethyl thiourea, tetramethyl thiourea,1,1-dibutyl thiourea, and 1,3-dibutyl thiourea; and mixtures thereof.Other secondary reducing agents may include cobalt (II) chloride,ferrous chloride, ferrous sulfate, hydrazine, hydroxylamine (dependingon the choice of oxidizing agent), salts of a dithionite or sulfiteanion, and mixtures thereof. Preferably, the reducing agent is an amine.

Suitable oxidizing agents will also be familiar to those skilled in theart, and include but are not limited to persulfuric acid and saltsthereof, such as sodium, potassium, ammonium, cesium, and alkyl ammoniumsalts. Additional oxidizing agents include peroxides such as benzoylperoxides, hydroperoxides such as cumyl hydroperoxide, t-butylhydroperoxide, and amyl hydroperoxide, as well as salts of transitionmetals such as cobalt (III) chloride and ferric chloride, cerium (IV)sulfate, perboric acid and salts thereof, permanganic acid and saltsthereof, perphosphoric acid and salts thereof, and mixtures thereof.

It may be desirable to use more than one oxidizing agent or more thanone reducing agent. Small quantities of transition metal compounds mayalso be added to accelerate the rate of redox cure. In some embodimentsit may be preferred to include a secondary ionic salt to enhance thestability of the polymerizable composition as described in U.S. Pat.Publication No. 2003/0195273 (Mitra et al.).

The reducing and oxidizing agents are present in amounts sufficient topermit an adequate free-radical reaction rate. This can be evaluated bycombining all of the ingredients of the composition except for theoptional filler, and observing whether or not a hardened mass isobtained.

Typically, the reducing agent, if used at all, is present in an amountof at least 0.01% by weight, and more typically at least 0.1% by weight,based on the total weight (including water) of the components of thecomposition. Typically, the reducing agent is present in an amount of nogreater than 10% by weight, and more typically no greater than 5% byweight, based on the total weight (including water) of the components ofthe unfilled composition.

Typically, the oxidizing agent, if used at all, is present in an amountof at least 0.01% by weight, and more typically at least 0.10% byweight, based on the total weight (including water) of the components ofthe composition. Typically, the oxidizing agent is present in an amountof no greater than 10% by weight, and more typically no greater than 5%by weight, based on the total weight (including water) of the componentsof the unfilled composition.

The reducing or oxidizing agents can be microencapsulated as describedin U.S. Pat. No. 5,154,762 (Mitra et al.). This will generally enhanceshelf stability of the composition, and if necessary permit packagingthe reducing and oxidizing agents together. For example, throughappropriate selection of an encapsulant, the oxidizing and reducingagents can be combined with an acid-functional component and optionalfiller and kept in a storage-stable state. Likewise, through appropriateselection of a water-insoluble encapsulant, the reducing and oxidizingagents can be combined with an fluoro-aluminosilicate (FAS) glass andwater and maintained in a storage-stable state.

A redox cure system can be combined with other cure systems, includingphotoinitiator systems or with a composition such as described U.S. Pat.No. 5,154,762 (Mitra et al.).

In another embodiment of the present disclosure, the initiator systemcomprises free radical-generating thermal initiators. Thermal initiatorsinclude organic peroxides (e.g., benzoyl peroxide), azo compounds,quinones, nitroso compounds, acyl halides, hydrazones, mercaptocompounds, pyrylium compounds, imidazoles, chlorotriazines, benzoin,benzoin alkyl ethers, diketones, phenones, and mixtures thereof.Examples of suitable thermal initiators are VAZO 52, VAZO 64 and VAZO 67azo compound thermal initiators, all available from DuPont. Preferredthermal initiators include benzoyl peroxide, dicumylperoxide, andandazobisisobutyronitrile (AIBN).

Nanofiller

The hardenable compositions of the disclosure can be formulated with oneor more nanofillers that may impart desirable wear and aestheticproperties (e.g., tooth like color to mask the underlying metal).Suitable nanofillers include either acid reactive or non-acid reactivenanofillers and may include, but are not limited to silica; zirconia;oxides of titanium, aluminum, cerium, tin, yttrium, strontium, barium,lanthanum, zinc, ytterbium, bismuth, iron, and antimony; andcombinations thereof. More typical nanofillers may include zirconia(ZrO₂); oxides of titanium (e.g., TiO₂), and oxides of yttrium (e.g.,Y₂O₃); and other metal oxides with high refractive indices. In preferredembodiments, the nanofiller comprises an oxide of titanium. As usedherein, “high refractive index” means a refractive index of typically atleast 1.5, and more typically of at least 2.0. Titania and zirconia areparticularly useful nanofillers, as they have very high refractiveindices, and will require less weight of material than a lowerrefractive index material to match the refractive indices appropriately.

The nanofillers typically have an average particle size of at most 100nanometers and more typically at most 50 nanometers. Such nanofillerstypically have an average particle size of at least 2 nanometers, moretypically at least 5 nanometers, and even more typically at least 10nanometers. In some embodiments, the nanofiller is in the form ofnanoclusters, typically at least 80 percent by weight nanoclusters. Inother embodiments, the nanofiller is in the form of a combination ofnanoparticles and nanoclusters. Often a portion of the surface of thenanofiller is silane treated or otherwise chemically treated to provideone or more desired physical properties. Additional suitable nanofillersare disclosed in U.S. Pat. No. 6,387,981 (Zhang et al.) and U.S. Pat.No. 6,572,693 (Wu et al.), U.S. Publication No. 2008/0293846 (Craig etal.), as well as International Publication Nos. WO 01/30305 (Zhang etal.), WO 01/30306 (Windisch et al.), WO 01/30307 (Zhang et al.), and WO03/063804 (Wu et al.). Filler components described in these referencesinclude nanosized silica particles, nanosized metal oxide particles, andcombinations thereof.

Typically, the nanofillers of the present disclosure are non-pyrogenicfillers, however pyrogenic fillers can be added as optional additives tothe dental compositions.

The amount of nanofiller should be sufficient to provide a hardenablecomposition having desirable mixing and handling properties beforehardening and good physical and optical properties after hardening.Typically, the nanofiller represents at least 0.1 wt-%, more typicallyat least 5 wt-% or 10 wt-%, and most typically at least 20 wt-% based onthe total weight of the composition. Typically, the nanofillerrepresents at most 60 wt-%, more typically at most 50 wt-%, and mosttypically at most 40 wt-%, based on the total weight of the composition.

Pigments & Other Fillers

The hardenable compositions of the present disclosure may furtherinclude pigments. A tooth-colored pigment can be achieved, for example,by using a mixture of titanium dioxide and iron oxide. The titaniumdioxide and iron oxide pigments can be used in varying amounts dependingon the shade of tooth enamel desired to be reproduced. For example, 15wt-% to 55 wt-% titanium dioxide, and 0.01 wt-% to 4.5 wt-% iron oxide,based on the total weight of the hardenable composition, give a naturaltooth enamel appearance to the coating. Additional pigments or colorantscan be optionally added to the starting coating powders to color-matchthe polymeric coating to a desired tooth color.

In addition to the nanofiller and pigment components, the hardenablecompositions of the present disclosure can also optionally include oneor more other fillers. Such fillers may be selected from one or more ofa wide variety of materials suitable for the use in dental and/ororthodontic compositions.

The other filler can be an inorganic material. It can also be acrosslinked organic material that is insoluble in the resin component ofthe composition, and is optionally filled with inorganic filler. Thefiller should in any event be nontoxic and suitable for use in themouth. The filler can be radiopaque or radiolucent. The filler typicallyis substantially insoluble in water.

Examples of suitable inorganic fillers are naturally occurring orsynthetic materials including, but not limited to: quartz; nitrides(e.g., silicon nitride); glasses derived from, for example, Zr, Sr, Ce,Sb, Sn, Ba, Zn, and Al; feldspar; borosilicate glass; kaolin; talc;titania; low Mohs hardness fillers such as those described in U.S. Pat.No. 4,695,251 (Randklev); and silica particles (e.g., submicronpyrogenic silicas such as those available under the trade designationsAEROSIL, including “OX 50,” “130,” “150” and “200” silicas from DegussaAG, Hanau, Germany and CAB-O-SIL M5 and TS 720 silica from Cabot Corp.,Tuscola, Ill.). Examples of suitable organic filler particles includefilled or unfilled pulverized polycarbonates, polyepoxides, and thelike.

Suitable non-acid-reactive filler particles are quartz, submicronsilica, and non-vitreous microparticles of the type described in U.S.Pat. No. 4,503,169 (Randklev). Mixtures of these non-acid-reactivefillers are also contemplated, as well as combination fillers made fromorganic and inorganic materials.

The surface of the filler particles can also be treated with a couplingagent. Suitable coupling agents includegamma-methacryloxypropyltrimethoxysilane,gamma-mercaptopropyltriethoxysilane, gamma-aminopropyltrimethoxysilane,and the like. Examples of useful silane coupling agents are thoseavailable from Crompton Corporation, Naugatuck, Conn., as SILQUEST A-174and SILQUEST A-1230. For some embodiments of the present disclosure thatinclude other fillers the compositions may include at least 1% byweight, more preferably at least 2% by weight, and most preferably atleast 5% by weight other filler, based on the total weight of thecomposition. For such embodiments, compositions of the presentdisclosure preferably include at most 75% by weight, more preferably atmost 65% by weight, and even more preferably at most 55% by weight otherfiller, based on the total weight of the composition.

When the polymer composition contains an ethylenically unsaturatedcompound and at least one filler, it is generally present in an amountof at least 15% by weight, more typically at least 25% by weight, andmost typically at least 35% by weight ethylenically unsaturatedcompounds, based on the total weight of the filled composition. Thecompositions of the present disclosure typically include at most 95% byweight, more typically at most 90% by weight, and most typically at most80% by weight ethylenically unsaturated compounds, based on the totalweight of the filled composition.

When the composition contains an ethylenically unsaturated compound withacid functionality, it is generally present in an amount of at least 1%by weight, more typically at least 3% by weight, and most typically atleast 5% by weight ethylenically unsaturated compounds with acidfunctionality, based on the total weight of the unfilled composition.The compositions of the present disclosure typically include at most 80%by weight, more typically at most 70% by weight, and most typically atmost 60% by weight ethylenically unsaturated compounds with acidfunctionality, based on the total weight of the unfilled composition.

Other Additives

Optionally, compositions of the present disclosure may contain solvents(e.g., alcohols (e.g., propanol, ethanol), ketones (e.g., acetone,methyl ethyl ketone), esters (e.g., ethyl acetate), other nonaqueoussolvents (e.g., dimethylformamide, dimethylacetamide, dimethylsulfoxide,1-methyl-2-pyrrolidinone)), or mixtures thereof.

Compositions of the present disclosure may further include core-shellpolymer compounds. A core-shell compound includes a soft core comprisinga rubber or elastomeric polymer surrounded by a shell comprising a morerigid polymer. Such compounds may reduce the shrinkage of thecomposition on polymerization. Exemplary core-shell polymer compoundsare discussed in U.S. Publication No. 2005/0124762. (Cohen et al.).

If desired, the compositions of the disclosure may contain additivessuch as indicators, dyes (including photobleachable dyes), inhibitors,accelerators, viscosity modifiers, wetting agents, antioxidants,tartaric acid, chelating agents, buffering agents, stabilizers,diluents, and other similar ingredients that will be apparent to thoseskilled in the art. Surfactants, for example, nonionic surfactants,cationic surfactants, anionic surfactants, and combinations thereof, mayoptionally be used in the compositions. Useful surfactants includenon-polymerizable and polymerizable surfactants. Additionally,medicaments or other therapeutic substances can be optionally added tothe hardenable compositions. Examples include, but are not limited to,fluoride sources, whitening agents, anticaries agents (e.g., xylitol),remineralizing agents (e.g., calcium phosphate compounds and othercalcium sources and phosphate sources), enzymes, breath fresheners,anesthetics, clotting agents, acid neutralizers, chemotherapeuticagents, immune response modifiers, thixotropes, polyols,anti-inflammatory agents, antimicrobial agents, antifungal agents,agents for treating xerostomia, desensitizers, and the like, of the typeoften used in dental compositions.

Combination of any of the above additives may also be employed. Theselection and amount of any one such additive can be selected by one ofskill in the art to accomplish the desired result without undueexperimentation.

Exemplary Composition of the Polymeric Layer Disposed on the CeramicMaterial & Spherical Microparticles

Suitable hardenable compositions for use in the polymeric layer disposedon the ceramic material (i.e., the basecoat) typically include apolymerizable component, a photoinitiator, a thermal initiator, ananofiller, a pigment, and a filler. Particularly suitable polymerizablecomponents for use in the basecoat include UDMA,phenoxyethylmethacrylate, and combinations thereof. Hardenablecompositions coated on wall surfaces below the height of contourpreferably include at least one flexible monomer or multimethacrylateoligomer. For basecoat hardenable compositions of the present disclosurethat include fillers (nanofillers & other fillers) the compositions mayinclude at least 1% by weight, more preferably at least 2% by weight,and most preferably at least 5% by weight filler, based on the totalweight of the composition. For such embodiments, compositions of thepresent invention preferably include at most 75% by weight, morepreferably at most 65% by weight, and even more preferably at most 55%by weight filler, based on the total weight of the composition.

Preparation of Polymer Compositions

The polymer compositions useful in the abrasion resistant hybrid coatingof the present disclosure can be prepared by combining all the variouscomponents using conventional mixing techniques. The resultingcomposition may optionally contain fillers, solvents, water, and otheradditives as described herein. Typically, photopolymerizablecompositions of the disclosure are prepared by simply admixing, under“safe light” conditions, the components of the inventive compositions.Suitable inert solvents may be employed if desired when affecting thismixture. Any solvent may be used which does not react appreciably withthe components of the inventive compositions. Examples of suitablesolvents include acetone, dichloromethane, isopropyl alcohol, ethanol,and butanone.

The amounts and types of each ingredient in the polymer compositions maybe adjusted to provide the desired physical and handling propertiesbefore and after polymerization. For example, the polymerization rate,polymerization stability, fluidity, compressive strength, tensilestrength and durability of the dental material typically are adjusted inpart by altering the types and amounts of polymerization initiator(s)and the loading and particle size distribution of filler(s). Suchadjustments typically are carried out empirically based on previousexperience with dental materials.

The components of the composition can be included in a kit, where thecontents of the composition are packaged to allow for storage of thecomponents until they are needed.

Coating the Dental Article

Prior to depositing the abrasion resistant hybrid coating, the targetsurface(s) (i.e., the portion of the article to be coated) of the dentalarticle may be primed (e.g., abraded, etched, particles deposited) toenhance the bond between the coating and the metal substrate surface. Inone embodiment, the target surfaces may be first sandblasted as known inthe art by, for example, the method shown in U.S. Pat. No. 5,024,711 toGasser et al. The target surfaces may be microblasted with an aluminumoxide sand, such as ROCATEC Pre, available from 3M ESPE. In someembodiments, the target surface may be subsequently treated with asilica-modified aluminum oxide, such as ROCATEC Plus, also availablefrom 3M ESPE. Alternatively, the outer surface may be treated withROCATEC Plus or other silica-modified aluminum oxide without priortreatment with ROCATEC Pre.

In another embodiment, the target surface of the dental article isprimed or otherwise modified by etching with a strong acid such ashydrochloric acid. Additional useful etchants include nitric acids,hydrofluoric acids, ferric chlorides, sodium hydroxides, andcombinations thereof. Although not wishing to be bound by theory, theroughening (i.e., priming) of the target surface by acid-etch orsandblast creates greater surface area and may strengthen the abrasionresistant hybrid coating bond to the chosen metal substrate.

The target surface may also be coated with a diamond-like glass (DLG),such as those described in U.S. Pat. No. 6,696,157 to David et al, aspart of the priming process. DLG is an amorphous carbon system includinga substantial quantity of silicon and oxygen that exhibits diamond-likeproperties. DLG may be deposited onto at least a portion of the targetsurface by plasma deposition or other techniques known to those havingskill in the art.

Once the target surface of the dental article has been primed, theceramic material may be deposited according to methods well known in theart, including, but not limited to, plasma spraying (i.e., thermalspraying), and powder coating followed by sintering. The ceramicmaterial is directly bonded, by e.g., an intimate chemical or mechanicalinteraction, to the target surface. In certain preferred embodiments,the ceramic layer is made to include a smooth surface by, for example,using higher temperatures & smaller colloidal particles in the plasmaspray. In one embodiment, the ceramic layer is deposited after primingand silanization and/or treatment with Zirconate as described below. Inembodiments wherein a discontinuous ceramic layer is contemplated, thepattern (e.g., alternating gaps & ceramic deposits) may be createdduring the ceramic application (by e.g. lithography, masking) or afterapplication of the ceramic layer (by e.g., laser ablation). For example,a curable resin can be applied in a grid, or waffle, pattern by aprinting process. A layer of ceramic deposited on top of thispre-applied pattern, by thermal spraying, sputtering, or a similarprocess, will conform to the pre-existing pattern, creating a similarpatterned structure on the surface of the dental article.

Alternatively, a thermally-sprayed layer of ceramic can be appliedthrough a metal mask containing apertures in a pattern to be replicatedon the underlying substrate. The mask may be disposed between the plasmaspray mechanism and the dental article. The ceramic material may then besprayed through the apertures, leaving portions of the outer surfaceuncoated and accordingly forming a discontinuous ceramic layer. Onlythat portion of the spray passing through the mask will actually depositon the surface of the dental article.

Additionally or alternatively, the pattern or porosity may be created bysubsequent laser ablation or sandblasting of targeted portions of thedeposited ceramic layer. The laser used for converting (e.g.,perforating or cutting) the ceramic layer article may be any suitableconventional laser. While many laser types may be suitable for theablating of the ceramic coated articles described herein, high densitygain media lasers such as solid state lasers, are particularlypreferred. High density gain media lasers can span the infrared to theultraviolet portion of the light spectrum, and also offer high peakpower and high continuous power. Theses lasers can be composed of twotypes of gain media: insulators (e.g., Nd:YAG to Ti:Sapphire) andsemiconductor (e.g., GaAs to Lead Salt). One preferred example of thistype of laser is Nd:YVO₄ or neodymium-doped yttrium vanadate laser, andits shorter wavelength harmonics.

An additional bonding layer may be deposited on the ceramic layer and/orthe surface of the dental article once the ceramic material has beendeposited on the target surface. The ceramic coated dental article mayundergo silanization by, for example, spray or bath after the sandblastor acid-etch abrasion procedure. Exemplary useful silanes include, butare not limited to, 3M ESPE Sil, available from 3M ESPE andmethacryloxypropyltrimethoxy silane, available under the tradenameGENIOSIL GF-31, from Wacker Chemical, Adrian, Mich. Alternatively oradditionally, the primed dental article may be exposed (e.g., by sprayor bath) to Zirconate coupling agents available from KenrichPetrochemicals, Bayonne, N.J.

If a hardenable composition includes phosphorylated monomers, it may beunnecessary to include a bonding layer on the target surface of thedental article/ceramic layer after priming.

The first layer of hardenable composition can be applied usingconventional techniques, including, but not limited to, dip coating,spray coating, spin coating, brush coating, and lithographic printing.

Thickness gradients and occlusal coatings may be created, for example,by directional spraying only the targeted portion of the crown withceramic, hardenable composition, or combination of the two so thatsubstantially none of a particular coating is applied below the heightof contour. Use of the spherical microparticles on substantially onlythe occlusal surface may also create a gradient.

In preferred embodiments, the hardenable composition is deposited on theceramic layer prior to curing. In embodiments wherein the hardenablecomposition includes a photoinitiator, a curing light, such as a VISILUXModel 2500 blue light gun (3M Co., St. Paul, Minn.) or a ELIPARFreelight 2 LED CuringLight (available from 3M ESPE Dental Products, St.Paul, Minn.) is generally required to irradiate the hardenablecompositions and initiate hardening (i.e., polymerization).Alternatively, an irradiating chamber may be used, such as a VISIO BetaVario Light Curing Unit (available from 3M ESPE Dental Products, St.Paul, Minn.

In embodiments wherein the hardenable composition comprises a thermalinitiator, heat may be used to initiate the hardening of free radicallyactive groups. Examples of heat sources suitable for curing includeinductive, convective, and radiant heat sources. Thermal sources shouldbe capable of generating temperatures of at least 40° C. and at most150° C. under normal conditions or at elevated pressure.

In certain embodiments wherein the hardenable composition comprises aphotoinitiator and a thermal initiator, the curing process includes bothirradiation and exposure to heat.

The spherical microparticles, can be added in any manner known to thoseskilled in the art for adding particles to a polymeric layer. Thespherical microparticles can be mixed into a wet (i.e., at leastpartially uncured) coating or scattered on top of a wet coating. Forexample, the spherical microparticles can be applied by a pelletdispenser which applies or sprinkles the microparticles on top of apolymeric layer which is still at least partially uncured. Withoutwishing to be bound by theory, the microparticles may adhere to the atleast partially uncured layer and at least a portion of themicroparticles may “sink” into the layer.

Several types of scattering machines can be used to accomplish theuniform sprinkling or dispensing of microparticles. In certainembodiments, the scattering machine has a rotating or applicator roll(engraved or knurled) at the bottom of the hopper. A stationary orrotary brush is used to remove microparticles particles from thedispensing or applicator roll. A shaker screen may be used under thehopper for uniform distribution of the microparticles. The knurl size,the dispensing or applicator roll speed, the brush position, the speedof the rotary brush, and the speed and the size of the shaker screenshould all be selected based on the amount and the size of themicroparticles to be used.

Additional layers of hardenable composition can be applied to the firsthardenable composition and spherical microparticles surface using theconventional techniques discussed above. Once all desired layers ofhardenable compositions have been deposited, each layer of hardenablecomposition are hardened to the extent possible (i.e., fully cured)according to techniques described above.

As noted above, the abrasion resistant hybrid coating of the presentdisclosure provides desirable aesthetic properties, such as closeapproximation of tooth color. The following parameters form the basis ofthe color determination of the coated dental article: Opacity value O:Measure of the transparency (0% is completely transparent, 100% isopaque), L*-value: Brightness (100: complete reflection; 0; noreflection); a*-value: Red-green shift (+a: red; −a: green); b*-value:yellow-blue shift (+b: yellow; −b: blue).

The L*-value of a coated dental article is preferably greater than 60,more preferably greater than 75, and even more preferably greater than80. The abrasion resistant hybrid coating may also be tailored to theshades on the VITA shade guide. The a* value of a coated dental articleis within the range of −3 to 13. The b* value of a coated dental articleis within the range of 10 to 35.

In certain embodiments, the abrasion resistant coating can maintaindesirable flexibility. One method of determining flexibility includesthe bending of a 150 micron thick metal coupon around a mandrel. Themetal coupon is preferably made of the same metal used on the outersurface of the dental article and includes a deposited abrasionresistant coating. Preferably, a coated coupon can bend 180 degreesaround an 8 millimeter mandrel without cracking of the coating. Morepreferably, a coated coupon can bend around a 4 millimeter mandrel, andeven more preferably a 2 millimeter mandrel without cracking of thecoating.

In another embodiment of the disclosure, a crown or a plurality ofcrowns (potentially of varying sizes) may be provided in a kit with thecomponents of the abrasion resistant hybrid coating. The crown(s) maypreferably be provided in the kit pre-primed (i.e., the surface has beenroughened according to techniques described below). The kit may furtherinclude ceramic material, spherical microparticles, and one or morehardenable dental compositions. The coating components may be providedseparately or already deposited on the crown surface. Such a kit mayallow a practitioner to tailor the particular location and aesthetics ofthe coating on the crown. The kit may also include other componentsincluding, but not limited to, cements, brushes, and other tools toapply the coatings.

Illustrative Embodiments

1. A method for coating a dental article comprising:

providing a body comprising a metal substrate;

depositing a ceramic material on at least a portion of the surface ofthe body, wherein said depositing forms a ceramic layer;

depositing at least one hardenable composition comprising apolymerizable component on at least a portion of the ceramic layer,wherein depositing at least one hardenable composition forms a firstpolymeric layer; and

depositing a plurality of microscale spherical particles on at least aportion of the first polymeric layer, wherein the plurality of ceramicparticles are at least partially embedded in the first polymeric layer.

2. The method of embodiment 1 further comprising priming a surface ofthe body, wherein priming at least a portion of a surface comprises:

depositing a layer of diamond-like glass on at least a portion of thesurface.

3. The method of embodiment 1, further comprising priming a surface ofthe body, wherein priming a surface comprises:

exposing at least a portion of the surface to a strong acid orsandblasting at least a portion of the surface.

4. The method of any one of embodiments 1 to 3, further comprisingapplying a bonding layer to at least a portion of the outer surface,wherein the bonding layer is selected from the group consisting ofsilane and zirconate.

5. The method of embodiment 1, wherein depositing the ceramic layercomprises creating a continuous ceramic layer over at least a portion ofthe surface.

6. The method of embodiment 1, wherein the dental article is a stainlesssteel crown having a height of contour, and wherein the ceramic materialis deposited substantially above the height of contour.

7. The method of embodiments 1-4 and 6, wherein depositing the ceramiclayer comprises forming a discontinuous ceramic layer.

8. The method of embodiment 7, wherein the medical article is astainless steel crown having a height of contour and wherein forming adiscontinuous ceramic layer comprises forming the discontinuous layer onthe outer surface substantially above the height of contour.9. The method of embodiment 7, wherein forming the discontinuous ceramiclayer comprises ablating at least a portion of the ceramic layer.10. The method of any one of embodiments 1-9, wherein the ceramicmaterial is selected from the group consisting essentially of: alumina,zirconia, yttria, yttria-stabilized zirconia, porcelain, andcombinations thereof.11. The method of embodiments 1-10, wherein depositing the ceramicmaterial comprises plasma spraying the ceramic material on a surface ofthe body.12. The method of any of the preceding embodiments, wherein thespherical particles comprise inorganic particles.13. The method of embodiments 1-12, wherein the average microparticlediameter is at least 5 microns and no greater than 200 microns.14. The method of embodiment 13, wherein the average microparticlediameter is as least 50 microns and no greater than 100 microns.15. The method of embodiments 1-14, wherein the combined thickness ofthe ceramic layer and the first polymeric layer is at least the averagemicroparticle diameter.16. The method of any one of the preceding embodiments, wherein thepolymeric component comprises at least one (meth)acrylate monomer.17. The method of embodiment 16, wherein the polymerizable component isselected from the group consisting of phenoxoyethyl methacrylate,urethane dimethacrylate, polyethylene glycol methacrylate, polypropyleneglycol methacrylate, triethyleneglycol dimethacrylate, the diglycidylmethacrylate of bisphenol A, and combinations thereof.18. The method of embodiments 1-17, wherein at least one hardenablecomposition comprises an initiator system, filler, and a pigment,wherein the filler comprises a nanofiller.19. The method of embodiment 18, wherein the initiator system comprisesa photoinitiator and a thermal initiator.20. The method of embodiments 18-19, wherein the filler is present at nogreater than 55 weight percent by weight of the composition.21. The method of embodiment 20, wherein the filler comprises a fumedsilica particle.22. The method of embodiments 18-21, wherein the pigment selected fromthe group consisting of titanium dioxide, iron oxide, and combinationsthereof.23. The method of embodiment 22, wherein the pigment is present at aweight of no greater than 55% by weight of the polymer.24. The method of any of the previous embodiments, further comprisingdepositing one or more additional hardenable compositions.25. The method of any of the previous embodiments, wherein the thicknessof the coating at a cervical margin of the crown is less than thethickness of the coating on the occlusal surface.26. The method of any one of the preceding embodiments, wherein thehardenable composition further comprises flexible monomers,multimethacyrlate oligomers, and combinations thereof.27. The method of embodiment 1, further comprising

irradiating at least a portion of the surface; and

exposing at least a portion of the surface to heat.

28. A dental article comprising:

a crown having a height of contour;

an abrasion resistant coating on at least a portion of the crown, thecoating layer comprising:

-   -   a ceramic layer comprising a ceramic material disposed on at        least a portion of the outer surface of the crown;    -   at least one polymeric layer disposed on at least a portion of        the ceramic layer, wherein the at least one polymeric layer        comprises at least one hardened dental composition comprising at        least one polymerizable component; and    -   a plurality of spherical microparticles embedded within at least        one polymeric layer.        29. The dental article of embodiment 28, wherein at least one of        the ceramic material and spherical microparticles are disposed        substantially above the height of contour.        30. The dental article of any one of embodiment 28-29, wherein        the ceramic material is selected from a group consisting of        alumina, zirconia, yttria, yttria-stabilized zirconia,        porcelain, and combinations thereof.        31. The dental article of embodiments 28-30, wherein the ceramic        layer is a discontinuous ceramic layer.        32. The dental article of embodiment 31, wherein the        discontinuous ceramic layer extends over at least a portion of        the occlusal surface substantially above the height of contour.        33. The dental article of embodiments 28-32, wherein the        thickness of the ceramic layer is no greater than 151 microns.        34. The dental article of embodiments 28-33, wherein the        spherical microparticles comprise inorganic microparticles.        35. The dental article of embodiments 28-34, wherein the        inorganic particles are selected from a group consisting of        alumina, zirconia, yttria, yttria-stabilized zirconia,        porcelain, and combinations thereof.        36. The dental article of embodiments 28-35, wherein at least        one spherical particle of the plurality of spherical particles        is in contact with the surface of the crown.        37. The dental article of embodiments 28-36, wherein said        spherical microparticles are present in an amount of from about        5% by weight to about 75% by weight, based on the weight of the        coating layer.        38. The dental article of embodiment 37, wherein said spherical        microparticles are present in an amount of from about 10% by        weight to about 50% by weight, based on the weight of the        coating layer.        39. The dental article of embodiments 28-37, wherein thickness        of the coating is at least the average microparticle diameter.        40. The dental article of any one of the preceding embodiments,        wherein the hardenable composition comprises an initiator        system, filler, and a pigment.        41. The dental article of embodiment 40, wherein the        polymerizable component is selected from the group consisting of        phenoxoyethyl methacrylate, urethane dimethacrylate,        polyethylene glycol methacrylate, polypropylene glycol        methacrylate, triethyleneglycol dimethacrylate, the diglycidyl        methacrylate of bisphenol A, and combinations thereof.        42. The dental article of embodiment 41, wherein the        polymerizable component is selected from the group consisting of        phenoxylethylmethacrylate, urethane dimethacrylate, and        combinations thereof.        43. The dental article of any one of the previous embodiments,        wherein the polymerizable component further comprises a        core-shell polymer compound.        44. The dental article of embodiments 40-43, wherein the        initiator system comprises a photoiniator and a thermal        initiator.        45. The dental article of embodiments 40-44, wherein the filler        is present at no greater than 20 weight percent by weight of the        composition.        46. The dental article of embodiments 40-44, wherein the pigment        is selected from the group consisting of titanium dioxide, iron        oxide, and combinations thereof.        47. The dental article of embodiment 46, wherein the pigment is        present at a weight of no greater than 55% by weight of the        polymer.        48. The dental article of embodiment 40-44, wherein at least one        hardened composition further comprises flexible monomers,        multimethacyrlate oligomers, and combinations thereof.        49. The article of embodiments 28-48, wherein the abrasion        resistant coating comprises a thickness gradient.        50. The article of embodiments 28-49, further comprising a        diamond-like glass layer deposited on at least a portion of the        outer surface.        51. The article of embodiment 28-50, further comprising a        bonding layer deposited on at least a portion of the outer        surface, wherein the bonding layer comprises a component        selected from the group consisting of silane and zirconate.        52 A kit comprising:

a crown

a ceramic material; and

at least one hardenable dental composition comprising a polymerizablecomponent, an initiator system, a pigment, and filler; and

a plurality of spherical microparticles; and

at least one of a cement, a brush, and instructions for application ofthe ceramic material, spherical microparticle, and hardenable dentalcomposition.

53. The kit of embodiment 52, wherein the stainless steel crown furthercomprises a diamond-like glass layer on at least a portion of the outersurface.

54. The kit of embodiments 52 or 53, wherein the ceramic compositioncomprises a ceramic chosen from the group consisting of alumina,zirconia, yttria, yttria-stabilized zirconia, porcelain, andcombinations thereof.

55. The kit of embodiments 52-54, wherein the polymerizable component isselected from the group consisting of phenoxoyethyl methacrylate,urethane dimethacrylate, polyethylene glycol methacrylate, polypropyleneglycol methacrylate, triethyleneglycol dimethacrylate, the diglycidylmethacrylate of bisphenol A, and combinations thereof.56. The kit of embodiments 52-55, wherein the bonding layer is selectedfrom the group consisting of silane and zirconate.

The complete disclosures of the patents, patent documents, andpublications cited herein are incorporated by reference in theirentirety as if each were individually incorporated. Variousmodifications and alterations to this invention will become apparent tothose skilled in the art without departing from the scope and spirit ofthis invention. It should be understood that this invention is notintended to be unduly limited by the illustrative embodiments andexamples set forth herein and that such examples and embodiments arepresented by way of example only with the scope of the inventionintended to be limited only by the claims set forth herein as follows.

We claim:
 1. A dental article comprising: a crown having a height ofcontour; an abrasion resistant coating on at least a portion of thecrown, the coating layer comprising: a ceramic layer comprising aceramic material disposed on at least a portion of the outer surface ofthe crown; at least one polymeric layer disposed on the entire ceramiclayer, wherein the at least one polymeric layer comprises at least onehardened dental composition comprising at least one polymerizablecomponent; and a plurality of spherical microparticles embedded withinat least one polymeric layer; wherein the dental article is malleable.2. The dental article of claim 1, wherein at least one of the ceramicmaterial and spherical microparticles are disposed substantially abovethe height of contour.
 3. The dental article of claim 1, wherein theceramic material is selected from a group consisting of alumina,zirconia, yttria, yttria-stabilized zirconia, porcelain, andcombinations thereof.
 4. The dental article of claim 1, wherein theceramic layer is a discontinuous ceramic layer.
 5. The dental article ofclaim 4, wherein the discontinuous ceramic layer extends over at least aportion of the occlusal surface substantially above the height ofcontour.
 6. The dental article of claim 1, wherein the thickness of theceramic layer is no greater than 151 microns.
 7. The dental article ofclaim 1, wherein the microparticles are selected from a group consistingof alumina, zirconia, yttria, yttria-stabilized zirconia, porcelain, andcombinations thereof.
 8. The dental article of claim 1, wherein thepolymerizable component is selected from the group consisting ofphenoxyethyl methacrylate, urethane dimethacrylate, polyethylene glycolmethacrylate, polypropylene glycol methacrylate, triethyleneglycoldimethacrylate, the diglycidyl methacrylate of bisphenol A, andcombinations thereof.
 9. The article of claim 1, wherein the abrasionresistant coating comprises a thickness gradient.